This invention relates to a head component of an orthopaedic joint prosthesis.
Shoulder and hip joint prostheses include a convex head component and a concave socket component. The head component can be provided on a stem component which can be implanted in the femur or the humerus. In this construction, the socket component is fixed against movement by implantation in the acetabulum or the glenoid respectively. Especially in shoulder prostheses, it is also known for the socket component to be provided on a stem component (for implantation in the humerus) for articulation with a fixed convex head component (which is implanted in the glenoid).
A modular component which comprises a head component and a stem component can be assembled using a mating tapered spigot and socket assembly. For example, the stem component can have a tapered spigot, and a correspondingly tapered socket can be formed in the head component. Such assembly arrangements are well known.
The formation (spigot or socket as the case might be) which is provided in the head component might be located eccentrically. This can enable the head component to be offset relative to the axis of the stem component. The orientation of the offset can be adjusted by rotating the head component relative to the stem component.
It can be difficult to determine the angular orientation of the head component relative to another with which it is to be assembled for use.